This project has been designed to understand the epidemiology of the risks for transmission of the hepatitis C virus (HCV) through unsafe drug injection and evaluate methods to reduce transmission. The study protocol applies an interdisciplinary epidemiological approach that fuses into laboratory-based research the real-world observations on drug injection practices to analyze (1) the potential for HCV transmission resulting from the use of HCV-contaminated injection equipment, (2) the duration of HCV viability in injection equipment of equipment, (3) the potential for disinfectants to inactivate HCV, and (4) the potential for exposure to infectious HCV in various drug preparation and injection practices common in parts of the world where the HCV epidemic among injection drugs users is still rapidly increasing. The laboratory assay takes advantage of a newly developed in vitro assay for HCV proliferation that employs whole virions and the handling of injection paraphernalia in the laboratory will be informed by oversight from medical anthropologists who have first-hand observational experience of drug injection practices. Epidemiological analysis and dissemination of the results will be used to inform prevention programs and individuals at risk for transmitting or becoming infected with HCV about the step that can be taken to reduce transmission. PUBLIC HEALTH RELEVANCE: This project is directly relevant to public health since the results will be used provide information needed to control the epidemic of hepatitis C virus transmission among injection drug users.